Anti H1- and anti H2-premedication.

Histamine-release responses in clinical conditions show a wide range of severity, from a single spot of erythema or a wheal up to a life-threatening reaction or the death of the patient. To demonstrate the efficiency of Hiand HE-blockade in preventing histamine-induced anaphylactic and anaphylactoid reactions, a series of controlled trials was carried out in patients, volunteers and dogs presenting histamine-release responses of all three grades of severity (table I). Both the histamine-releasing drugs and the histamine H1and HE-receptor antagonists had to be chosen for these trials according to a series of well-conceived and strict criteria. For the histamine H1and HE-receptor antagonists, the criteria for selection included potency, selectivity, duration of action, clinical experience with the drug and the availability both for tlae oral and the intravenous routes. For the HE-receptor antagonist, selection was not difficult since, at the time of the first trials, cimetidine was the only available drug on the market. However, the choice of the Hi-receptor antagonist was very difficult. Dimethindene (Forhistal ® in the USA, Fenistil ® in Europe) was chosen since it is very potent [12, 14], highly selective [11, 14], its duration of action was long enough for 2-3 h of operation, but not too long-lasting to interfere with postoperative recovery, and the drug did not release histamine in man [6]. Five controlled clinical and experimental trials were conceived and carried out in the last six years, a synopsis of which has been compiled in table II. Materials and methods of all these trials have been described in previous communications [4, 9, 10, 13]. In